It's a BIOS message - nothing to do with whether or not you've got a Win98 CD. It's failing to "see" the hard disk for some reason and so it's attempting to boot from floppy.
If it all works fine otherwise there's probably not much you can do. I'd check the cables are all well seated and I'd poke around in the BIOS setup to see if it's set to "Hard disk auto-detect". It might be worth turning that off and entering the actual hard disk spec there instead - but this all depends on the BIOS.
"Ancient at two years old"??? Bet you don't think of your aircraft like that...